to make a machine, system, or device start working or operating
Pressing the red button will activate the alarm.
The remote control wouldn't activate the television no matter how hard she tried.
to enable software, a digital account, or a feature so it can be used, often by entering a code or going online
You need an internet connection to activate the new game.
She clicked the link in the email to activate her account.
to cause a chemical, biological, or cellular substance to become reactive or start functioning
Ultraviolet light can activate vitamin D production in the skin.
The enzyme needs calcium ions to activate.
to place a military unit, facility, or plan into active service
The government decided to activate the national guard after the hurricane.
The army will activate the reserve unit for the joint exercise.
to cause a device, machine, weapon, or system to stop operating or functioning.
Please deactivate your account if you no longer wish to use the service.
The security guard had to deactivate the alarm before letting the workers inside.
✦ Early 20th century: from de- (expressing removal or reversal) + activate.
